U IIH Iffi IH I Iffi II H IHfl IIH I

PERPUSTAKAAN UMP

U IIH Iffi IH I Iffi II H IHfl IIH I 0000092805

EFFECT OF PALM OIL FUEL ASH (POFA) TOWARD FOAM CONCRETE COMPRESSIVE STRENGTH AND MICROSTRUCTURE

NUR FADILAH HANIM BINTI MOHD NASIR

A Report submitted in partial fulfillment of the requirements for the award of the de gree of

B.ENG. (HONS) CIVIL ENGINEERING

Faculty of Civil Engineering and Earth Resources

Universiti Malaysia Pahang

June 2014

vi

ABSTRACT

Malaysia is well known as the main crude palm oil producer and exporter in the

world. Million tons of agro wastes such as palm oil fuel ash (POFA) is being produced

every year with no commercial return on it. Due to the pozzolanic behavior possessed

by POFA, it could be significance when the POFA is being recycled and used in

production of lightweight foamed concrete (LWFC). Thus, the aim of this research is to

study the effects of POFA on engineering properties and microstructure of LFC with

1 600kg/m3 until 1800kg/rn3 of density in terms of compressive strength, porosity,

scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). Four

types of foamed concrete were prepared with different percentage LWC with 0%, 10%,

20% and 30%. All the specimens were water cured before being tested. At the 20%

concrete containing of POFA had a highest strength which is 11.2, 15.15 and 29.20 MPa

and lower porosity is 14.99, 11.94 and 9.54. It is proved that the percentage of porosity

is lest and the strength of the other specimen is higher. Besides, it was found that the

micro structure of LFC was denser and the pore size of the structure was refined with the

presences of POFA, compared with that of control mix. Effective consumption of POFA

as a pozzolanic material in concrete can decrease the cost of concrete production, save

environmental and also can solve the landfill problem

vii

ABSTRAK

Malaysia terkenal sebagai pengeluar minyak sawit mentah utarna clan pengeksport

terbesar di dunia. Berjuta-juta tan sisa pertanian seperti abu bahan api kelapa sawit

(POFA) telah dihasilkan setiap tahun tanpa pulangan kornersial keatasnya. Oleh kerana

berlaku tindakbalas pozzolanic yang dimiliki oleh POFA, ia menjadi penting apabila

POFA dikitar sernula dan digunakan dalam pengeluaran konkrit berbusa ringan (LFC).

Oleh itu , tujuan kajian mi adalah untuk mengkaji kesan POFA pada sifat-sifat

kejuruteraan clan struktur mikro LWFC dengan 1600kg/rn3 sehingga 1800kg/rn3

ketumpatan dari segi kekuatan mampatan , keliangan, mikroskop irnbasan elektron (

SEM ) dan analisis gravimetrik terma (TGA) . Empat jenis konkrit berbusa telah

disediakan dengan peratusan yang berbeza diantaranya ialah LWC dengan 0 %, 10 %,

20 % dan 30 % POFA, kesemua kuib direndarn dalarn air sebelum diuji . Didapati

konkrit yang mempunyai peratusan POFA sebanyak 20 % mempunyai kekuatan

mampatan yang tertinggi iaitu 11.2 , 15.15 dan 29.20 MPa clan keliangan yang lebih

rendah adalah 14.99 , 11.94 dan 9.54. la membuktikan bahawa peratusan keliangan

rendah dan kekuatan mampatan konkrit yang mempunyai peratusan POFA sebanyak

20% adalah lebih tinggi daripada peratusan POFA yang lain. Selain itu, melalui struktur

rnikro telah mendapati bahawa LWFC yang mempunyai peratusan POFA sebanyak 20

% adalah lebih padat, berbanding dengan konkrit biasa. Penggunaan yang berkesan

pada POFA sebagai bahan pozzolana dalam konkrit boleh mengurangkan kos

pengeluaran konkrit, memelihara alarn sekitar dan juga boleh menyelesaikan rnasalah

tapak pelupusan.

TABLE OF CONTENTS

CHAPTER TITLE PAGE

SUPERVISOR'S DECLARATION

STUDENT'S DECLARATION

DEDICATION iv

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF FIGURES xii

LIST OF TABLE xiii

LIST OF SYMBOLS! ABBREVIATIONS xiv

CHAPTER 1 INTRODUCTION

11 Introduction 1

1.2 Problem Statement 2

1.3 Objective of Study 3

1.4 Scope of the Study 3

1.5 Significance of the Study 4

vi"

1.6 Layout of Thesis

CHAPTER 2 LITERETURE REVIEW

2.1 Introduction 5

2.2 Type of Aerated Concrete 6

2.3 Ordinary Portland Cement Concrete 7

2.3.1 Main Compounds of Portland Cement 8

2.3.2 Chemical Composition of Ordinary Portland 8

Cement

2.4 Palm Oil Fuel Ash 9

2.4.1 Definition Of Palm Oil Fuel Ash 9

2.4.2 Characteristics of POFA 10

2.4.3 Chemical Properties of POFA 12

2.4.4 Use of POFA in Concrete 13

2.5 Form Agents 15

2.6 Pozzolanic Material 16

2.7 Pozzolanic Reaction 17

CHAPTER 3 METHODOLOGY

3.1 Introduction 18

3.2 Methodology Flow 19

lx

4

3.3 Experimental Plan 20

3.4 Concrete Specimens Mixing Ingredients 21

3.4.1 Sand 21

3.4.2 Water 22

3.4.3 Ordinary Portland cement (OPC) 22

3.4.4 Palm Oil Fuel Ash (POFA) 23

3.4.5 Foaming Agent 24

3.5 Concrete Mix Design 26

3.5.1 Process of Concrete Making 27

3.5.2 Mixing 27

3.5.3 Casting 28

3.5.4 Curing 28

3.6 Number of Specimens 29

3.7 Testing of Concrete 29

3.7.1 Compressive Strength Test 30

3.7.2 Porosity Test 32

3.7.3 Scanning Electron Microscope (SEM) Test 33

3.7.4 Thermal Gravimetric Analysis Test 34

CHAPTER 4 RESULTS AND DISCUSSION

x

4.1 Introduction 35

xi

4.2 Chemical Composition on POFA 35

4.3 Compression Strength Test Results 36

4.3.1 Discussion on Compressive Strength 41

4.4 Effect of POFA content on Porosity Test 42

4.5 Scanning Electron Microscope (SEM) Test of POFA 44

4.6 Thermal Gravimetric Analysis (TGA) 46

CHAPTER 5 CONCLUSION AND RECOMMENDATIONS

5.1 Introduction

51

5.2 Conclusion

51

5.3 Recommendation

52

REFERENCES

54

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Flow chart for the palm oil process 15

3.1 Methodology Flow Chart 19

3.2 Research process flow 20

3.3 Sand 21

3.4 Ordinary Portland Cement (OPC) 22

3.5 Palm oil fuel ash (POFA) 24

3.6 Foam Generator 25

3.7 Foaming Agents 25

3.8 Cement Mixer 28

3.9 Compressive strength test machine 31

3.10 Hitachi VP-SEM S-3700N 33

3.11 Coating of specimen before SEM analysis 34

4.1 Average for compressive strength for all percentages 37

4.2 Compressive strength for sample 1 38



4.5 Porosity of concrete with difference percentage 43

4.6 SEM picture for POFA partial at structure for 0% 44




4.10 Thermal Gravimetric Analysis Graft at 0% POFA 47




xii

LIST OF TABLE

TABLE NO. TITLE

PAGE

xlii

2.1 Main Compound of Ordinary Portland Cement

2.2 General Composition Limits of Portland Cement

2.3 Physical Characteristics of as received and the Blended

Ground POFA

2.4 Chemical Composition of POFA Used In Various

Researches

3.1 General Composition Limits of Portland Cement

3.2 Mixture mix design

3.3 The numbers of sample prepared.

4.1 The chemical compositions of the POFA and OPC

4.2 Relationship between averages of compressive strength

of mortar with different percentage of cement

replacement

8

9

11

13

23

26

29

36

41

LIST OF SYMBOLS I ABBREVIATIONS

C-S-H Calcium Silicate Hydrate

OPC Ordinary Portland Cement

POFA Palm Oil Fuel Ash

SEM Scanning Electron Microscope

TGA Thermal Gravimetric Analysis

UMP University Malaysia pahang

w/b water-to-binder ratio

Si02 Silicon dioxiode

Al203 Aluminum oxide

Fe2O3 Ferric oxide

CaO Calcium oxide

MgO Magnesium oxide

S03 Sulphur oxide

Na2O Sodium oxide

K20 Potassium oxide

LOI Loss of ignition

DTG Derivative Thermogravimatric

Ca(OH)2. Calcium Hydroxide

CaCO3 Calcium Carbonate

xiv

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

Malaysia is widely known around the world as a one of the largest product of palm

oil. Palm oil is extracted from copra and fruit of the palm oil tree. Next after the extraction

process, waste industry products like shells, fibers and palm oil are burnt to the boil water,

to extraction process in palm oil mills. More two hundred palm oil mills operating only in

Malaysia (Hussin and Awal, 1997). POFA in Malaysia has inspired research towards

integrating this material as cement replacement in concrete production. POFA as

replacement in concrete will indirectly minimize the environmental issues, scarcity of raw

materials and the important thing can consumption of energy.

Waste generation from this industry reported that more two million tons of solid

waste of palm oil residue as empty fruit bunches palm oil and also shells are produced

annually (Office of the Agricultural Economics, 2002). At the same time, the increasing

demand of construction material especially concrete has lead towards the use of natural

aggregated. In order to reduce the consumption of this natural aggregate and to ensure

environmental sustainability, they use of alternative constituent in concrete.

In conclusion, most of the concrete produced nowadays are multi component

containing one, two or more admixtures in additional to the basic component such as water,

cement, fine and coarse aggregate. The creation of the new material will definitely offer as

extra boost to the palm oil industry

1.2 PROBLEM STATEMENT

Malaysia which is the major palm oil exported palm oil processing factory for a

long time. So far the discovery on the utilization of palm oil fuel ash (POFA) as partial

cement replacement in concrete research is limited to production of normal concrete

(Hussin and Abdul Awal, 1996) and high strength concrete (Sata et al.2004). The dumping

of palm oil fuel ash (POFA) has become a missive problem to palm oil because this

wastage has not been recycled or reused in any work, this problem also been highlighted by

Tay and Show(1990), who stated that this ash also caused environmental problems and

potential health hazard. In this study aerated concrete will use to combine with palm oil

fuel ash (POFA).

Aerated concrete has a very low thermal conductivity that makes it an excellent fire

protection property (Narayanan & Ramamurthy, 2000b) than normal concrete. It is also

known that tones of industrial waste are produced worldwide every day that cause

environmental problems. Aerated concrete is generally regarded as a green and

environmentally cause the main components of aerated concrete are sand, cement, water,

aluminum powder and also Palm Oil Fuel Ash (POFA) and that there is o environmental

pollution.

ru

1.3 OBJECTIVE OF STUDY

The objectives of the study are:

i. To determine the compressive strength of foam concrete by using POFA

content as partial cement replacement in aerated concrete.

ii. To investigate the Microstructure of foam concrete by using POFA as

cement replacement material.

iii. To identify the POFA toward concrete hydration product.

1.4 SCOPE OF STUDY

The purpose of the research is an attempt to incorporate POFA in the production of

lightweight concrete specifically known as aerated concrete. The density of the concrete

must around 1800kg/rn3

At the first stage of the laboratory work, the mix proportion of POFA as partial

cement replacement in aerated concrete which is used as the control subject is developed.

The set of test consist of water, sand, aluminum powder, cement and various content of

POFA which replaces the cement partially by weight. The mix proportion percentage is

0%, lO%,20% and also 30%.

The concrete mixes were cast and poured into the mould. All specimens were

subjected to water curing. In this study, the test was used 100mm x 100mm x 50mm cube

size for porosity test and compressive strength was used 100mm x 100mm x 100mm, was

measured at 7, 28 and 90 days. For Scanning Electron Micrograph (SEM) and Thermal

Gravimetric Analysis (TGA) test was conduct at concrete age 60 days.

5

1.5 SIGNIFICANT OF STUDY

Concrete is a one of important material in construction. Nowadays many

development and modification have been made to replace concrete to industrial waste such

as POFA. Findings from the research would provide more information on the properties of

aerated concrete various content of POFA as partial cement replacement. Moreover, the

usage of partial sand replacement material in concrete could reduce the amount of natural

sand used in construction project and also can minimize the cost of the construction

material.

1.6 LAYOUT OF THESIS

This thesis paper consists of five (5) parts. The first part is chapter 1 of research that

elaborate briefly on the project introduction, problem statement, objective, scope of study,

significance of study and also layout of thesis. Than for chapter 2 discusses the findings

and previous work done by other researchers regarding the concrete properties and

pozzolanic materials that are used in concrete. chapter 3 is methodology part presents the

methodology, material and experimental approach used in this study. Next, chapter 4 is

elaborates and discusses on the finding and result from the experimental that has been done

in accordance to the methodology. Finally, chapter 5 is presents the conclusion of the all

results and outlines recommendation for future research.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

Concrete is one of the oldest manufactured construction material used in

construction of various structures globally until now. Concrete production has certainly

enormousness of natural resources such as which has caused substantial environmental

losses. Therefore, it is seen that integrating palm oil fuel as as partial sand replacement

material would reduce the utilization of natural sand in concrete production.

During recent decades, Ahmad et al. (2005) reported that, palm oil fuel ash which

contain siliceous compositions and able to react as pozzolanic materials to produced a

stronger and denser concrete when it is used as partial cement replacement material and

about thousands of tons of palm oil fuel ash (POFA) are produced yearly by operation of

200 palm oil mills in Malaysia and most of these POFA are normally disposed for landfill

without any commercial return (Awal, 1997).

In this fast paced world, addition of waste materials in concrete has rapidly

increased due to the booming of construction industry. This is parallel to the effort in

reducing consumption of energy from industries due to the greenhouse effect, high energy

cost and diminishing energy sources in the world.

me

i-iowever, continuous researcn or concrete material nas resuitea many types of

concrete having unique characteristic to fulfill the current construction industry demand.

One of the concrete that becoming famous nowadays is aerated concrete due to it's

lightness and versatility. Aerated concrete quickly spread to different parts of the world

after the end of the Second World War (Bave, 1983). It is produced in various types and

methods for the use of construction in many countries. Aerated concrete which is light,

contribute to the reduction of building dead weight thus resulting in more economic

structural design (Short & Kinniburgh, 1978) and (Narayanan & Ramamurthy 2000b).

Besides that, other researchers Short & Kinniburgh (1978) and Holt & Raivio (2005) added

that the lightness of the aerated concrete structure makes it easier to be transported and

handled. In addition, aerated concrete also has a very low thermal conductivity that makes

it an excellent fire protection property (Taylor, 2000 and Narayanan & Ramamurthy,

2000b). Short & Kiimiburgh (1978) and Holt & Raivio (2005) supported the above fact and

also highlighted.

2.2 TYPE OF AERATED CONCRETE

Aerated concrete is also known as cellular aerated concrete, foamed concrete,

cellular concrete or gas concrete. According to Tam et.al (1987), the type of concrete is

essentially an aerated cement mortar or paste made by introducing gas or air in the form

(diameters from 0.1 to 1.0mm) into a plain a cement paste or mortar mix during the mixing

process.

According to the past research, Narayanan & Ramamurthy (2000b), aerated

concrete can be divided to two types that are gas concrete and foamed concrete. Aerated

concrete is classified based upon the method of Gas concrete is produced using gas-forming

materials, which is mixed into lime or cement mortar during the liquid or plastic stage,

resulting in a mass of increased volume and when the gas escapes, leaves a porous structure

(Narayanan & Ramamurthy, 2000b). It is a mixture of very fine aggregates, water, and

cement with final addition pore-forming chemical that will produce air-voids within the

7

aqueous mix at atmospheric pressure resulting it to expand to certain extent depending on

the amount of gas produced and entrapped inside the structure.

Foamed concrete is manufactured by entertaining relatively large volumes of air

into the cement paste by the use of a chemical foaming agent (Kearsley & Wainright,

2001). In other words, it is a mortar mix containing air voids that been produced by adding

foaming agents which plays the role of creating pores within the concrete without

chemically reacting to the cement.

2.3 ORDINARY PORTLAND CEMENT CONCRETE

There are many advantages of concrete such as build in fire resistance, high

compressive strength and also low maintenance, (Choo, 2003). It has been widely used

because of it is rich resources of raw materials, good performance, simple production

process, high strength and durability, low price and also can be combined with

reinforcement to produce a strong reinforced concrete structure. Since global warming has

emerged as the most serious environmental issues, the concrete industry will not be the new

types of concrete • manufactured with expensive materials and special methods but highly

concrete mixtures and low cost containing largest possible amounts of industrial and urban

by-products that are suitable for partial replacement of Portland cement, drinking water and

virgin aggregate (Metha,2004).

During concrete mixing, the cement and water will cost the surface of the coarse

and fine aggregates. When the concrete induce the hydration reaction, the specimen will

hardens and gains strength to form the concrete. According Metha (2001), each one of these

Concrete primary constituents, to a extent has an environmental impact and give rise to

different sustainabilfty issues. Normal concrete has a comparatively low tensile strength

and for structural application.

2.3.1 Main Compounds of Portland cement

Raw material used in manufacturing Ordinary Portland Cement such as alumina,

iron oxide and more. Table 2.1 shown main compound of Ordinary Portland Cement

according Neville,2009).

Table 2.1 : Main Compound of Ordinary Portland cement

Name of Compound Oxide Composition Abbreviation Compound

Composition%

Tricalcium Silicate 3CaO.Si02 C3S 42-67

Dicalcium Silicate 2CaO.SiO2 C2S 8-31

Tricalcium Silicate 3CaO.Al203 C3A 5-14

Tetracalcium 4CaO.Al203.Fe2O3 CAF 6-12

Aluminoferrite

Sources: Neville, 2009

8

2.3.2 Chemical Composition of Ordinary Portland cement

Ordinary Portland cement mostly contained chemical compositions like alumina,

silica and limestone. The three type of chemical very important for the formulation of

calcium silicate hydrate during hydration process. Table 2 below shown the composition of

cement according (Neville,20 10).

Table 2.2: General Composition Limits of Portland cement

Oxide Content, %

CaO 60-67

Si02 17-25

Al203 3-8

Fe203 0.5 -6.0

MgO 0.5-4.0

Na2O 0.3-1.2

S03 2.0-3.5

Sources: Neville,2010

2.4 PALM OIL FUEL ASH (POFA)

2.4.1 Definition of Palm Oil Fuel Ash

In Malaysia POFA is a by-product produced in palm oil mill. After palm oil is

extracted from the palm oil fruit, both palm oil husk and palm oil shell are burned as fuel in

the boiler of palm oil mill. In practice, POFA produced in Malaysian palm oil mill is

dumped as waste without any profitable return (Sumadi & Hussin, 1995).

10

Generally, after combustion about 5% palm oil fuel ash by weight of solid wastes is

produced (Sata et.al , 2004). Since Malaysia is continuous to increase production of palm

oil, therefore more ashes will be produced and failure to find any solution in making use of

this by-product will' create severe environmental problems. The ash produced sometimes

varies in tone of colour from whitish grey to darker shade based on the carbon content in it.

The physical characteristic of POFA is very much influenced by the operating system in

palm oil factory. Chindaprasirt et al., (2007) stated that the increasing amount of palm oil

fuel ash disposed in landfills has noe becomes a burden and nuisance to the environment.

There will be approximately 20 tonnes of nut shells, 7 tonnes of fibers, and 25 tonnes of

empty bunches discharged from the mill for every 100 tonnes of fresh fruit bunches

processed (Tay, 1995). POFA is still considered as a nuisance to the environment and

disposed without being put for any other use as compared to other type of palm oil by-

product.

2.4.2 Characteristics of POFA

POFA is a pozzolanic materials as indicated by both physical properties and

chemical analysis (Awal and Hussin, 1997; Sumadi and Hussin, 1993). This characteristic

is crucial in determining the suitability of using POFA as a partial cement replacement in

concrete.

The physical properties of POFA are greatly influenced by the burning condition,

particularly burning temperature (Abdullah et al., 2006). Next, the rate of pozzolanic

reaction, hydration and development of POFA concrete strength depends on the fineness of

Particles. Underground POFA particles are mostly large, spherical and porous. In contrast,

the ground POFA generally consist of smaller crushed particles with irregular and angular

shape similar to the Portland cement (Chindaprasirt et al. 2007).

11

The chemical composition for pozzolanic material is grouped in between Class C

and Class F as specified in ASTMC618-92a (Awal & Hussin, 1997). Both physical

properties and chemical analysis indicated that POFA is a pozzolanic material (Awal &

Hussin, 1997; Sumadi & Hussin, 1993).

Usually, the grinding process reduces not only the particles size but also the

porosity of the POFA (Kiattikomol et al., 2001). Particles size of POFA can be reduced by

the grinding process in Los Angeles abrasion machine using mild steel bar instead of steel

ball (Abdullah et al. 2006). After grinding, POFA can be less porous with smaller particles

(Paya et al., 1996). The general physical properties of raw and ground POFA are presented

in Table 2.3 below.

Table 2.3 Physical Characteristics of as received and the Blended Ground POFA

Physical Properties

Ground POFA

Raw POFA

Texture

Powdery Hard, gritty, light, cellular

Shape

Round

Irregular

Appearance before ignition Grayish, powdery

Dark spongy

Appearance after ignition Brownish

Porous, grayish

Sources: Oyeleke Et Al., 2011

Particularly, as POFA contains lower lime content compared to OPC, large and

hence amount of POFA could not be used as partial cement replacement. This is due to the

lower content of calcium oxide which tends to hinder the hydration process which thus

would give negative impact towards the early strength development of concrete. However,

the chemical composition of POFA can still be varied because of the variability in the

12

nature of the product and because of various burning conditions due to different

implementation of operating in the palm oil mail.

Researchers (Awal et. Al., 1996 ; Abdullah et al., 2006) have classified POFA as a

class F pozzolan and POFA is quite rich in silica content while lime content is very low

compared to OPC (Awal and Hussin,1997). The justification was made based on the

percentage of CaO content in POFA. The major chemical composition of POFA is Si02

which contain about more than 50% of the constituents.

2.4.3 Chemical Properties of POFA

While the amount of POFA produced increase annually, allocation of transportation

cost and landfills for the disposal of POFA is not an effective way to manage the waste as

POFA has no commercial return value and it may lead to environmental problems in the

future (Tangchirapat et al., 2006). Studies from researchers such as Tay (1995), Hussin and

Awal (1997) and Tangchirapat et al.(2006) have proved that POFA can be reutilised as

cement replacement material or as aggregate in concrete due to the pozzolanic properties it

possesses. Supply of POFA from different palm oil mill will have separate chemical

properties. However, silica is still the major chemical composition in POFA. The chemical

composition of different POFA used in various research works are shown in Table 2.4

Table 2.4: Chemical Composition of POFA Used In Various Researches

Chemical Composition 1 Awal Tangchirapat Eldagal

Silicon dioxiode (Si02) 43.60 57.71 48.99

Aluminum oxide (Al203) 11.50 4.56 3.78

Ferric oxide (Fe203) 4.70 3.30 4.89

Calcium oxide (CaO) 8.40 6.55 11.69

Magnesium oxide (MgO) 4.80 4.23 1.22

Sulphur oxide (S03) 2.80 0.25

Sodium oxide (Na2O) 0.39 0.50 0.73

Potassium oxide (K20) 3.50 8.27 4.01

Loss of ignition (LOl) 18.00 10.52 10.51

Sources: AwaI,1997; Tangchirapat, 2007; Eldagal, 2008

2.4.4 Use of POFA in Concrete

According, Chindaprasirt et al. (2006) stated that the POFA can be applied as the

new pozzolic materials in concrete with an acceptable strength. That the optimum cement replacement by POFA is 20 % which if it is beyond this ratio, the compressive strength is

13

14

reduced and also tends to give higher permeability of concrete. However, it was suggested

to use finer POFA in order to achieve better strength of POFA concrete (Hussin and Awal,

1996). According to (Tay, 1990; Tay and Show, 1995), they revealed that the compressive

strength of concrete decrease as the POFA content increase. In the other researcher have

found that the concrete made with POFA exhibit a higher compressive strength than OPC

concrete (Tonnayopas et a!; 2006).

Besides that, the durability of concrete is one of the most important properties a side

from it is compressive strength because in concrete are mostly due to durability failures

rather than insufficient strength. The research conducted by Awal and Hussin (1997) have

becomes fruitful when they manage to enhance the durability of plain concrete thought the

integration of 20 % of POFA by weight of cement. However, the high strength concrete

containing ground POFA showed a better resistance to sulfate attack than normal POFA

concrete (Tangchirapat et al., 2009) which thereby indicate that the fineness influenced the

sulfate resistance of concrete.

Several studies were also conducted to investigate the effect of POFA towards the

carbonation of cement paste (Chindaprasirt and Rukzon, 2009). Awal and Hussin (1999)

have investigated concrete resistance to carbonation with and without ground POFA. They

have found that there is a little difference between the carbonation values of POFA and

OPC concrete. In addition, they have also mentioned that the results are not truly

conclusive because POFA concrete appears to be more sensitive to the exposure condition.

This situation indicates that the dryer the concrete, the deeper the carbonation in POFA

concrete. Therefore, it can be concluded that the POFA of greater fineness and appropriate

replacement percent should be used as supplementary cementing material in concrete in

order to improve the properties of POFA concrete.

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